1. Field of the Invention
This invention finds its greatest application in the field of finely crushed granular material and more particularly, the field of coal or ore mining.
2. Description of the Prior Art
The use of sampling devices for selectively taking samples of finely ground particulate material, such as coal or ore is well known. Certain types of these devices are shown in U.S. Pat. Nos. 632,713; 1,646,032; 3,433,078; 3,595,088, 3,939,714; and 4,215,579. Some of these devices are useful for grain products and some others are useful for fluid slurries. The latter are not necessarily useful with drier particulate matter. Each of these devices of the prior art has deficiencies which makes it less than optimal for the selection of samples of granular material.
In the practical application of the coal sampling device, it has been found that the feed stream from which the sample is taken consists of fine, moist granules which have a tendency to stick to surfaces on which they fall. Thus, the particular problem faced in the selection of coal samples is not usually found in the gathering of samples of dry grains, seeds or cereals or in the gathering of samples from liquid slurries.
One of the main drawbacks of the devices of the prior art teachings is the fact that the sample is not taken directly from the source which selects the sample but the sample is deposited on a chute or inclined trough to flow toward a receptacle. This deficiency is easily seen in those devices where the selected sample flows down a chute to discharge or where the sample can flow against the inside surface of the selection drum or wheel. In these cases, the samples taken may stick to the surface of the chute or the inside surface of the drum and require a cleaning operation for the chute or trough. In additon, the sample may build up even to the point of clogging up the chute.
The present invention avoids these problems by permitting the sample to flow directly into a bag or other receptable without an intermediate chute or discharge surface to traverse. In addition, the apparatus of the present invention is fully enclosed so that the sample is collected without concern for air drafts which are present in well ventilated coal mines. The dust problem which is always present in a coal mine is diminished because the apparatus is enclosed.
The device can be easily adjusted to vary the size of the sample and the number of samples selected per unit of time.
The device of the invention is used in an environment in which the selection process takes place over an 8-hour period and takes samples from a primary stream of 400 tons per hour.